OS-5192 need faster clock_gettime
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Joshua M. Clulow <jmc@joyent.com>
Reviewed by: Ryan Zezeski <ryan@zinascii.com>

@@ -25,11 +25,11 @@
 /*
  * Copyright (c) 2010, Intel Corporation.
  * All rights reserved.
  */
 /*
- * Copyright 2015 Joyent, Inc.
+ * Copyright 2016 Joyent, Inc.
  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
  */
 
 #include <sys/types.h>
 #include <sys/thread.h>

@@ -245,11 +245,29 @@
         }
 
         kpreempt_enable();
 }
 
+#if !defined(__xpv)
 /*
+ * Configure per-cpu ID GDT
+ */
+static void
+init_cpu_id_gdt(struct cpu *cp)
+{
+        /* Write cpu_id into limit field of GDT for usermode retrieval */
+#if defined(__amd64)
+        set_usegd(&cp->cpu_gdt[GDT_CPUID], SDP_SHORT, NULL, cp->cpu_id,
+            SDT_MEMRODA, SEL_UPL, SDP_BYTES, SDP_OP32);
+#elif defined(__i386)
+        set_usegd(&cp->cpu_gdt[GDT_CPUID], NULL, cp->cpu_id, SDT_MEMRODA,
+            SEL_UPL, SDP_BYTES, SDP_OP32);
+#endif
+}
+#endif /* !defined(__xpv) */
+
+/*
  * Multiprocessor initialization.
  *
  * Allocate and initialize the cpu structure, TRAPTRACE buffer, and the
  * startup and idle threads for the specified CPU.
  * Parameter boot is true for boot time operations and is false for CPU

@@ -428,10 +446,14 @@
 #endif
                 cp->cpu_m.mcpu_idle_cpu = cpu_idle;
 
         init_cpu_info(cp);
 
+#if !defined(__xpv)
+        init_cpu_id_gdt(cp);
+#endif
+
         /*
          * alloc space for ucode_info
          */
         ucode_alloc_space(cp);
         xc_init_cpu(cp);

@@ -1484,10 +1506,14 @@
         /*
          * Initialize our own cpu_info.
          */
         init_cpu_info(CPU);
 
+#if !defined(__xpv)
+        init_cpu_id_gdt(CPU);
+#endif
+
         cmn_err(CE_CONT, "?cpu%d: %s\n", CPU->cpu_id, CPU->cpu_idstr);
         cmn_err(CE_CONT, "?cpu%d: %s\n", CPU->cpu_id, CPU->cpu_brandstr);
 
         /*
          * Initialize our syscall handlers